/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.hop.core.util;

import java.util.Arrays;

/**
 * A similarity algorithm indicating the percentage of matched characters between two character
 * sequences.
 *
 * <p>The Jaro measure is the weighted sum of percentage of matched characters from each file and
 * transposed characters. Winkler increased this measure for matching initial characters.
 *
 * <p>This implementation is based on the Jaro Winkler similarity algorithm from <a
 * href="http://en.wikipedia.org/wiki/Jaro%E2%80%93Winkler_distance">
 * http://en.wikipedia.org/wiki/Jaro%E2%80%93Winkler_distance</a>.
 *
 * <p>This code has been adapted from Apache Commons Lang 3.3.
 */
public class HopJaroWinklerDistance {

  /** Represents a failed index search. */
  public static final int INDEX_NOT_FOUND = -1;

  private double j = 0D;
  private double jw = 0D;

  public Double getJaroDistance() {
    return Double.valueOf(j);
  }

  public Double getJaroWinklerDistance() {
    return Double.valueOf(jw);
  }

  /**
   * Find the Jaro Winkler Distance which indicates the similarity score between two CharSequences.
   *
   * <pre>
   * distance.apply(null, null)          = IllegalArgumentException
   * distance.apply("","")               = 0.0
   * distance.apply("","a")              = 0.0
   * distance.apply("aaapppp", "")       = 0.0
   * distance.apply("frog", "fog")       = 0.93
   * distance.apply("fly", "ant")        = 0.0
   * distance.apply("elephant", "hippo") = 0.44
   * distance.apply("hippo", "elephant") = 0.44
   * distance.apply("hippo", "zzzzzzzz") = 0.0
   * distance.apply("hello", "hallo")    = 0.88
   * distance.apply("ABC Corporation", "ABC Corp") = 0.93
   * distance.apply("D N H Enterprises Inc", "D &amp; H Enterprises, Inc.") = 0.95
   * distance.apply("My Gym Children's Fitness Center", "My Gym. Childrens Fitness") = 0.92
   * distance.apply("PENNSYLVANIA", "PENNCISYLVNIA")    = 0.88
   * </pre>
   *
   * @param left the first String, must not be null
   * @param right the second String, must not be null
   * @return result distance
   * @throws IllegalArgumentException if either String input {@code null}
   */
  public void apply(final CharSequence left, final CharSequence right) {
    final double defaultScalingFactor = 0.1;

    if (left == null || right == null) {
      throw new IllegalArgumentException("Strings must not be null");
    }

    final int[] mtp = matches(left, right);
    final double m = mtp[0];
    if (m == 0) {
      j = 0D;
      jw = 0D;
    } else {
      j = (m / left.length() + m / right.length() + (m - mtp[1]) / m) / 3;
      jw = j < 0.7D ? j : j + Math.min(defaultScalingFactor, 1D / mtp[3]) * mtp[2] * (1D - j);
    }
  }

  /**
   * This method returns the Jaro-Winkler string matches, transpositions, prefix, max array.
   *
   * @param first the first string to be matched
   * @param second the second string to be matched
   * @return mtp array containing: matches, transpositions, prefix, and max length
   */
  protected static int[] matches(final CharSequence first, final CharSequence second) {
    CharSequence max;
    CharSequence min;
    if (first.length() > second.length()) {
      max = first;
      min = second;
    } else {
      max = second;
      min = first;
    }
    final int range = Math.max(max.length() / 2 - 1, 0);
    final int[] matchIndexes = new int[min.length()];
    Arrays.fill(matchIndexes, -1);
    final boolean[] matchFlags = new boolean[max.length()];
    int matches = 0;
    for (int mi = 0; mi < min.length(); mi++) {
      final char c1 = min.charAt(mi);
      for (int xi = Math.max(mi - range, 0), xn = Math.min(mi + range + 1, max.length());
          xi < xn;
          xi++) {
        if (!matchFlags[xi] && c1 == max.charAt(xi)) {
          matchIndexes[mi] = xi;
          matchFlags[xi] = true;
          matches++;
          break;
        }
      }
    }
    final char[] ms1 = new char[matches];
    final char[] ms2 = new char[matches];
    for (int i = 0, si = 0; i < min.length(); i++) {
      if (matchIndexes[i] != -1) {
        ms1[si] = min.charAt(i);
        si++;
      }
    }
    for (int i = 0, si = 0; i < max.length(); i++) {
      if (matchFlags[i]) {
        ms2[si] = max.charAt(i);
        si++;
      }
    }
    int transpositions = 0;
    for (int mi = 0; mi < ms1.length; mi++) {
      if (ms1[mi] != ms2[mi]) {
        transpositions++;
      }
    }
    int prefix = 0;
    for (int mi = 0; mi < min.length(); mi++) {
      if (first.charAt(mi) == second.charAt(mi)) {
        prefix++;
      } else {
        break;
      }
    }
    return new int[] {matches, transpositions / 2, prefix, max.length()};
  }

  public void reset() {
    j = 0D;
    jw = 0D;
  }
}
